The invention relates to a suction appliance for cleaning purposes, in particular, for cleaning floors, which comprises a dirt collecting container with a suction inlet and a suction outlet on which a filter is held, a suction unit for acting upon the dirt collecting container with negative pressure, a suction chamber between the suction unit and the filter with an external air inlet, via which external air can flow into the suction chamber to act upon the filter on the clean-space side, a valve device with a valve seat forming the external air inlet, and a valve body movable relative to the valve seat, the valve body in a closed position abutting sealingly on the valve seat and in an open position releasing the valve seat, and an actuating member, actuation of which causes the valve body to be transferred from the closed position to the open position.
In such a suction appliance, the external air inlet is closed by the valve device, i.e., the valve body assumes its closed position in which it abuts sealingly on the valve seat, during normal suction operation. The dirt collecting container can be acted upon with negative pressure via the suction chamber. This allows negative pressure to be generated at the suction inlet, in order to suck in suction material, for example, dirt or liquids, through it and deposit this in the dirt collecting container. During continuous suction operation, particles of dirt may accumulate on the filter and clog it. This results in a decrease in the negative pressure in the dirt collecting container and, consequently, in reduced suction power of the suction appliance.
To clean the filter, the user of a generic suction appliance can actuate the actuating member in order to transfer the valve body from the closed position to the open position in which it releases the valve seat. External air, for example, under atmospheric pressure, can flow into the suction chamber through the open external air inlet and act upon the filter to be cleaned on the clean-space side. Owing to the difference between the pressure of the external air and the negative pressure prevailing in the dirt collecting container, the filter to be cleaned is subjected to a pressure surge, as a result of which particles of dirt become detached from the filter and are deposited in the dirt collecting container. In addition, external air flows through the filter counter to the direction of flow prevailing during suction operation. This assists the cleaning of the filter. The valve body can then be transferred from the open position to the closed position again, and, therefore, the external air inlet closed, and normal suction operation can be continued.
Suction appliances of the kind mentioned at the outset have been found to work well in practice. However, it would be desirable if the suction result could be further increased.
The object of the present invention is to so develop a generic suction appliance that an improved suction result is obtained.